The invention relates to check valves for hydronic heating and cooling systems.
It is customary to install check valves on the outlet side of each circulator in a hydronic system, both to isolate each zone from others and to prevent gravity circulation through the system. Gravity circulation occurs as the result of cooler, denser fluid in the return lines of a particular zone "falling," suctioning heated, less dense fluid into the given zone. The check valves are usually sweated into the supply line of each zone, downstream of the circulator.
Check valves are also used in multiple-zone hydronic systems, to prevent backflow into a non-operating circulator zone from an adjacent operating zone.
Various forms of circulators are known. Some circulators employ a separate electrical motor coupled to a separate pump. Another form of circulator is the so-called "wet-rotor" circulator, in which the pump and motor are integrated, resulting in a more compact overall circulator unit. In a wet-rotor circulator, the rotor is supported within a rotor housing into which the fluid being circulated is allowed to enter (the fluid helps to lubricate the rotor bearings). The rotor housing is supported within a surrounding stator, which is sealed from the circulating fluid. An impeller, attached to the rotor, extends from the rotor housing into an impeller casing. Water entering the impeller casing flows from an inlet port to the eye of the impeller, and then outward to an outlet port. Servicing the motor or impeller is done by unbolting the motor housing from the impeller casing. This provides access to both the motor and the impeller, without disturbing connections between the impeller casing and the pipes to which it is connected.
The typical check valve is a separate unit installed downstream of the circulator. Service of such a check valve typically requires removing the valve from the pipe, and substituting a new unit.
Efforts have been made to integrate the check valve into the outlet port of the impeller casing (e.g., as suggested by dashed lines 22 in FIG. 1). But so installed, it is necessary to break the connection between the impeller or pump casing 12 and the pipes to which it is connected, and remove the pump casing, in order to remove the check valve. Only then can the check valve be slid out of the pump casing axially as suggested by arrow 24. This makes field replacement difficult and laborious. Because check valves in the hydronic circulator environment are subject to frequent clogging and failure there has long been a need for a check valve which could be easily and quickly replaced in the field.